Air cleaner



A. NUTTING April 10, 1945.

AIR CLEANER Filed Sept. 15, 1942 3 Sheets- Sheet l INVENTOR ARTHUR NUTTINq ATTORNEY April .10, 1945. -n 2,373,330

AIR CLEANER Filed Sept. 15, 1942 5 Sheets-Sheet 2 lNV ENTOR ARTHQRNUTTINCLI BY MAM ATTORNEY A. NUTTING April 10, 1945.

AIR CLEANER Filed Sept. 15, 1942 3 Sheets-Sheet 5 INVENTOR ARTHuR NunmqBY 0 e 7 z I ATTORNEY Patented Apr. 10, 1945 UNEED STATES AIR CLEANERArthur Nutting, Louisville. Ky., assignor to American Air FilterCompany, Inc., Louisville, Ky., a corporation of Delaware ApplicationSeptember 15, 1942, Serial No. 458,426

2 Claims.

. This invention relates to dust arrestors of the wet type wherein airis centrifuged against a water wetted surface to effect the removal ofits dust content.

The principal object of the invention is to provide a wet type dustarrestor having a high air handling capacity, a high air cleaningefiiciency and a low air flow resistance which arrestor is simple andinexpensive to construct, easy and inexpensive to operate and maintain.

The invention resides in the provision of a novel arrangement of bamesforming a path of sinuous shape for the fiow of air in combination withmeans for feeding both air and liquid to one end of the sinuous path atrates such that the air is intensively centrifuged in, and asubstantially continuous stream of liquid is air-propelled through, thepath. When the air velocity is high enough to effect intensivecentrifugal action in, and to propel a substantially continuous streamof liquid through, the path, it compels the liquid stream to form aliquid film extending from one end to the other of each concaveair-directing wall of each half cycle of the path and to form a liquidcurtain extending from the end of one film across the air stream to thebeginning of the next'film and it can be used to compel the liquidstream to form another liquid curtain extending from the end of the lastfilm across the air stream although the last film may be otherwisedirected. In this manner with a path of s shape for example, the air istwice centrifuged, twice scrubbed against a film of water and once ortwice forced to pass through a curtain of water with the result thatsubstantially all of its particles are thoroughly wetted and effectivelyremoved from the air flow.

An embodiment of the invention is illustrated in the accompanyingdrawings wherein:

Figure l is a front elevation of a work-cabinet provided with a dustarrestor embodying this invention;

Figure 2 is a section taken on line 2-2 of Figure 1;

Figure 3 is a fragmentary enlarged view of the baffle and water batharrangement shown in Figure 2; and

Figure 4 is a section corresponding to Figure 3 but showing an extendedbaflie arrangement.

The work cabinet, used to illustrate one application of the presentinvention, is of a type adapted for grinding or light-machiningmagnesium. Since the magnesium dust formed by such operations isexceedingly light, and highly explosive when dry, its separation fromair and ultimate collection is a serious and difficult problem. Thepresent invention not only solves this problem int-a very satisfactorymanner but'is admirably suited for general dust arrestor use.

In the work cabinet illustrated, an air stream or column enters the workspace of a work cabinet casing I through an inlet opening 2 and flowsdownwardly through the work space or inlet chamber 3 toward the spacebetween a liquid bath d and the lower end. of a partition 5 within thecasing. The air column impinges against the liquid bath 6 and sweepslaterally along the surface of that hath as it turns around the lowerend of the partition 5 to flow upwardly through the space lying on theother side of the partition. For convenience that portion of this spacewhich extends upwardly from the bath and adjacent the partition, istermed a bafile zone while the remainder thereof is termed an outletchamber 6. The'outlet chamber contain a pair of airdirectingwater-eliminating baffles l. The top of the outlet chamber dischargesupwardly into a blower B which is driven by a suitable motor M to createthe air column and which discharges the air to atmosphere. The blowerand motor may be conveniently mounted on the top of the casing i. Theinlet opening 2 of the casing provides access to the inlet chamber orwork space 3, which, for working purposes, is provided with a removablebottom grid- 0r grill-like work table 8 and a tool shelf 9. In magnesiumwork tables, it is desirable to minimize the explosive hazard; hence thework table and tool shelf are both preferably made of some non-sparkingma terial, such as hard wood.

In accordance with my invention an air centrifuging or bafliing means isarranged, in the baffie zone, to define a horizontal air inlet slot forsaid zone and to constrain the air column in said zone to pass in theform of a shallow ribbon from said slot upwardly along a path of sinuousshape which as illustrated i of general 8 form. The lower edge of theslot is positioned sufficiently below the static and operating levels ofthe liquid bath to insure the continuous supply of enough liquid forfilmand curtain-forming purposes. The blower is of suflicient capac-tyto move the ribbon of air along the S path at a velocity efiective notonly to subject said ribbon of air to intensive centrifugal action inthe lower and upper halve of said 8 path, but also to sweep a continuousstream of liquid into said path and to move it upwardly through thepath. At a velocity effective for these purposes, the liquid will notonly assume the form of a liquid film flowing along each concave wall tothe air discharge end thereof, but also assume the form of a liquidcurtain projecting across the air column either from the end of thefirst film or from the ends of each film as desired.

Accordingly a baiile member L (at the left), having an upwardlyextending concave air-directing surface or wall I0 is mounted on thecasing in a position such that its concave wall l0 defines the convexside of the lower half of the s path. The upper edge of baiiie member Lis disposed to discharge more or less obliquely across the centralportion of the 8 bath while its lower end is tangentially extendeddownwardly into the bath, at an angle approximating 15 to thehorizontal, for a distance which brings the extension below theoperating level of the bath. Another baiiie member R (at the right),having an upwardly extending convex and concave air-directing surface orwall, is mounted on the casing I and partition 5 in a position such thatits lower convex wall Ii defines the concave side of the lower half ofthe 8 path while its upper concave wall l2 defines the convex side ofthe upper hall of the 8 path. In other words, the convex wall ll oi! theR bame cooperates with the concave wall I0 of the L baiiie to form thelower half of the 8 path while the concave wall I2 of the R bai'ilecontinues upwardly from the convex wall ll thereof to form the upperhalf of the S path. The upper edge oi the R baiile, as illustrated, isdisposed to discharge across the path of the air column leaving the 8path, this column flowing upwardly through the outlet chamber 6.

In explaining the operation of this invention we will assume that, inFigure. 3, which is drawn more or less to quarter scale: the radii ofcurvatures of concave wall i0 and convex wall II respectivelyapproximate 2.5" and 0.56"; the distances across the .passage betweenconcave and convex members l0 and I i, at the narrowest and widestpoints respectively adjacent the entrance and central portions of the 8path approximate 1.5" and 2.6"; the radii of curvatures oi the lower,central and upper portions of concave wall II respectively approximate2.8", 10.0" and 2.5"; and the static liquid level extends approximately0.5" below the lowermost portion of the battle member R. With theseassumptions, upon the institution of an air flow approximating 500 c. f.m. for each horizontal foot of slot opening, the velocity willapproximate 4000'/min. at the narrowest section of the s path underneathconvex wall ll. At this velocity, the liquid level, on the inlet side,will drop'approximately 1.0" from the static level indicated to theoperating level indicated. The flow oi! air will further depress theoperating leveladjacent the entrance to the 8 path to an extentapproximating 0.25" causing such level to assume a slope of thecharacter indicated.

The head created by this depression in the operating level will tend tomaintain a continuous free flow of water into thev entrance of the 8path. This fiow will be at a substantial rate and will ordinarilyapproximate 16 to 16.5 gals. per minute for each horizontal foot of theentrance to the S path. The foregoing figures are given for the purposeof illustration and not 01' limitation. a

The air entering the 8 path will sweep the free flowing water onto theconcave wall 10 and form .a substanially continuous film of water onthat wall. This film is rapidly moved by the air along the wall III andfinally projected from the end oi that wall across the passage onto theconcave wall of member ii. The projected film forms a water curtainacross the air column and when precipitated on the concave wall 12 it Qagain forms a substantially continuous film,

which is moved rapidly by the air alongwall i2 and, in the structureillustrated, finally procurtain extending across the air dropping backinto the bath.

The air in impigning against the liquid bath as it enters the 8 pathwill, of course, entrain some water. This water, together with thecontained dust content of the air, is subjected to extremely intensivecentrifugal action in the lower hall! of the path 8, due to the shortradii of curvatures employed in forming this half of the passage. As aresult, a very substantial portion of its entrained water and dustcontent is deposited upon the film of water moving along concave wall l0and thus initially removed from the air column. When this precipitatedmatter is projected, in the form of a curtain extending across thecentral part of the 8 path, some of it will, of course, be again pickedup by the air stream but a surprisingly large percentage is not pickedup but is redeposited on the concave wall ll. The central curtainsubjects whatever dust is then contained in the air to further contactwith water which, if suc' cessiul, increases the likelihood that suchparticles will be removed in the upper half of the S path. During itsflow in the upper half, the air is again centrifuged tending to depositits remaining dust content and to redeposit the water and dust, which itpicked up from the central air curtain. In passing through the columnand second air curtain at the end of the S path the dust content of theair is again subjected to contact with water and again some water anddust may be entrained. However, when the air is finally discharged intothe relatively large outlet chamber 6, it very rapidly loses its highvelocity, and the lifting power occasioned thereby, with the result thatsubstantially all of its entrained water and water wetted dust will dropgravitationally into the bath through the removably mounted lint screenbasket la which, when removed, will carry with it the lint collecting inthat section of the bath.

The operating characteristics of an arrestor constructed in accordancewith this invention may be shown irom test data on the Figure 3structure having a slot one horizontal foot long. At 500 c. f. hi. thisdevice had a resistance of 4.6" of water column, a water flow of 16.2galsllmin. and a collecting efliiciency ranging from 93.2% to 95.5% on907 grams of bentonite clay particles 2 microns or less) when fed inconcentrations ranging from .46 to .93 grain per cubic foot of air. Itsair fiow resistance ranges from 4.0" to 6.0" of water column forairfiows ranging from 300 to 1000 c. f. in. All of the foregoing valuesare approximate.

The cleaning efliciency of the present arrestor in removing lint is evenhigher than the efliciencies above indicated. Not only is this true, butthis arrestor avoids the tendency of many dust arrestors to becomeclogged with lint since there are no spaces in the arrestor where lintcan collect and restrict the air flow. Furthermore, the lint removedfrom the air flow is deposited in the water bath at the bottom of theoutlet chamber 6 in which section of the bath it floats and from whichit cannot ordinarily return to the inlet section and there reenter theseparating passage.

The arrestor is not only a poor humidifier, having a humidifyingemciency approximating 25%, but surprisingly entrains very little water.This is largely due to the fact that water is not atomized at any time.The liquid curtains are not composed of atomized water articles but aremore or less in the form of sheets composed of relatively large drops ofwater. As a result, the simplest form of eliminator is effective toremove substantially all of the entrained water. Thus, the watereliminating baiiles l are sufiiciently effective, although theypractically subject the air to nothing more than a90 turn.

In Figure 3, the S passage progressively increases in area upwardly fromthe narrowest section at its bottom. This is not essential, but isdesirable since it decreases the air fiow resistance without noticeablyaffecting the dust collecting eiliciency.

The air flow resistance also increases progressively as the static waterlevel is progressively raised. While this level may extend flush with,or even higher than, the lower surface of convex wall I l, a staticlevel of the character indicated is recommended.

Although the liquid bath is shown and preferred as a means for feedingwater to the S passage, other liquid feeding means may be employed, suchas sprays. Whatever water feeding means is employed, it should bepositioned to feed water adjacent the slot to insure the early formationof a film on concave wall Ill.

When the discharge edge of concave wall 12 is disposed as indicated inFigure 3, a second liquid curtain is formed as previously stated. Thiscurtain may be eliminated, if desired, and the water at this pointdiverted from the air stream in any suitable manner. For example, thewater may be skimmed from the air fiow at this point by means well knownin this art and therefore not illustrated. The water thus diverted maybe returned to the water bath or otherwise disposed.

In the modification indicated in Figure 4, the S path is extendedthrough an additional 8 path by providing two addiLonal (right and left)baflle members respectively designated Y and Z. The lower W and X bafllemembers are identical to the L and R members shown in Figure 3 but arereversed in position. While the upper Y and Z bafile members may beduplicates of the corresponding lower baflles, as illustrated, each is aduplicate of the X baflle member. The spaces between the adjacent endsof the W and Y baifle members and the X and Z baflle membersrespectively are closed by wall members [3 and I4. With thisarrangement, upon the institution of an air flow effective to carry acontinuous stream of water upwardly through th double 8 passage formed,it will be evident that the air will be centrifuged-four times, scrubbedfour times, and forced to pass through water curtains.

It will be noted that the baflle means of each dust arrestor describedand illustrated herein is constructed and arranged to define ahorizontally-open slot-like air inlet at the bottom of the baflle zoneand a sinuous air passage of slot-like cross-sectional area extendingfrom the inlet slot to the outlet chamber. This sinuous air passage issubstantially free of abrupt changes in either direction orcross-sectional area; hence it constrains the air column flowing throughthe zone to pass in the form of a shallow, sinuous ribbon which issubstantially free of abrupt changes in thickness. Also, theconcavely-curved wall defining each convex side of the sinuous pathprovides a surface along which it is possible for a continuous liquidfilm to be air-propelled.

Having described my invention. 1 claim:

1. A dust arrestor comprising: a casing wherein an air stream or columnis adapted to move downwardly through an air inlet chamber to impingeagainst a bottom liquid bath as it turns to enter and pass upwardlythrough a baflle zone and thence into an outlet chamber; bafiie meansconstructed and arranged not only to divide the upper portion of saidliquid bath into supply and drainage sections underlying the inlet andoutlet chambers respectively and subject to the air pressures thereof soas to present low and high operating liquid levels respectively but alsoto define an upright s-shaped sinuous ai passage of slotlikecross-sectional area presenting a horizontally-open slot-like air inletat the bottom of the zone communicating with the inlet chamber and airoutlet slot at the top of the zone disposed to discharge air into theoutlet chamber at an upward inclination to the vertical and over thdrainage section, said passage being substantially free of abruptchanges in direction and crosssectional area so as to constrain the aircolumn in said zone to pass in the form of a shallow, sinuous ribbonwhich is substantially free of abrupt changes in thickness, said inletslot having its lower edge sufiiciently below the normal low operatinglevel of the supply section of said liquid bath for film-forming andcurtain-forming purposes and said bafile means including an upwardlyextending element having a concavelycurved air-directing wall and beingmounted on the casing in a position such that its concave wall definesthe convex sid of the lower half of the S-path and provides a surfacealong which a continuous liquid film may be air-propelled from the bathend of the wall to the other end thereof and an upwardly-extendingmember having a convexlyand a concavely-curved air-directing wallmounted on the casing in a position such that its convex Wall definesthe concave side of the lower half of the S-path, while its concave walldefines the convex side of the upper half of the S-path and provides asurface along which a continuous liquid film may be air-propelled to its3 upper end, the upper end of eachconcave wall terminating in adischarge edge; and air moving means operative to move said ribbon ofair along said path at a velocity efiective not only to subject saidribbon of air to intensive centrifugal action along each concave wallbut also to sweep a continuous stream of liquid from the supply sectionof said bath into said path and propel said stream upwardly through saidpath whereby said air ribbon forces the liquid stream to fiow in the lform of a continuous liquid film along each concave wall to thedischarge end thereof and in the form of a liquid curtain from the endof each film completely across the adjacent air flow, the first curtainextending to the beginning of the next film and the last curtaindraining into the drainage section of the bath.

2. The dust arrestor of claim 1 wherein the outlet slot is substantiallywider than the inlet slot; and the convex and concave walls of theupwardly extending member are relatively short and long respectivelywhile the concave wall of the upwardly extending element is ofintermediate length, these walls being spaced so that the area of theS-shaped passage progressively increases in the direction of air flowsubstantially throughout the length of the passage.

ARTHUR NUT'I'ING.

